Dissertations / Theses on the topic 'Discretization time varying system'

Sliding mode control (SMC) has been successfully applied to many practical control problems due to its attractive features such as invariance to matched uncertainties. The characteristic feature of a continuous-time SMC system is that sliding mode occurs on a prescribed manifold, where switching control is employed to maintain the state on the surface. When a sliding mode is realized, the system exhibits some superior robustness properties with respect to external matched uncertainties. However, the realization of the ideal sliding mode requires switching with an infinite frequency. Control algorithms are now commonly implemented in digital electronics due to the increasingly affordable microprocessor hardware although the essential conceptual framework of the feedback design still remains to be in the continuous-time domain. Discrete sliding mode control has been extensively studied to address some basic questions associated with the sliding mode control of discrete-time systems with relatively low switching frequencies. However, the complex dynamical behaviours due to discretization in continuous-time SMC systems have not yet been fully explored. In this thesis, the discretization behaviours of SMC systems are investigated. In particular, one of the most frequently used discretization schemes for digital controller implementation, the zero-order-holder discretization, is studied. First, single-input SMC systems are discretized, stability and boundary conditions of the digitized SMC systems are derived. Furthermore, some inherent dynamical properties such as periodic phenomenon, of the discretized SMC systems are studied. We also explored the discretization behaviours of the disturbed SMC systems. Their steady-state behaviours are discussed using a symbolic dynamics approach under the constant and periodic matched uncertainties. Next, discretized high-order SMC systems and sliding mode based observers are explored using the same analysis method. At last, the thesis investigates discretization effects on the SMC systems with multiple inputs. Some conditions are first derived for ensuring the

In recent years the problem of designing a feedback control law to stabilize a linear, time-varying uncertain system has received considerable attention. However, the problem is usually limited to the case of systems which satisfy the "matching" assumptions. Moreover, the question of the existence of a linear stabilizing control, if a nonlinear stabilizing control exists, is still unanswered. In the present work an attempt is made to design a stabilizing, linear, feedback control law for a specific second order, linear system which contains time-varying uncertainties into both the state and input matrices and does not satisfy the matching conditions. For specific values of the uncertainty bounds this system is quadratically stabilizable but not quadratically stabilizable via linear control.

Master of Science

Dynamic processes on real-world networks are time-delayed due to finite processing speeds and the need to transmit data over nonzero distances. These time-delays often destabilize the network's dynamics, but are difficult to analyze because they increase the dimension of the network.We present results outlining an alternative means of analyzing these networks, by focusing analysis on the Lipschitz matrix of the relatively low-dimensional undelayed network. The key criteria, intrinsic stability, is computationally efficient to verify by use of the power method. We demonstrate applications from control theory and neural networks.

We consider the solution of nonlinear optimal control problems subject to stochastic perturbations with incomplete observations. In particular, we generalize results obtained by Ito and Kunisch in [8] where they consider a receding horizon control (RHC) technique based on linearizing the problem on small intervals. The linear-quadratic optimal control problem for the resulting time-invariant (LTI) problem is then solved using the linear quadratic Gaussian (LQG) design. Here, we allow linearization about an instationary reference trajectory and thus obtain a linear time-varying (LTV) problem on each time horizon. Additionally, we apply a model predictive control (MPC) scheme which can be seen as a generalization of RHC and we allow covariance matrices of the noise processes not equal to the identity. We illustrate the MPC/LQG approach for a three dimensional reaction-diffusion system. In particular, we discuss the benefits of time-varying linearizations over time-invariant ones.

Dynamiken för en starkt accelerande robot har modellerats. Modellen linjäriseras så att roboten beskrivs som ett linjärt tidsvariabelt system. Denna representation beskriver roboten väl då robotens anblåsningsvinkel, vilket är vinkeln mellan robotkroppen och robotens hastighet, är liten. Eftersom det ej är möjligt att mäta alla robotens tillstånd har en observatör tagits fram i form av ett Kalmanfilter. Problematik vid framtagandet av observatören diskuteras i rapporten. Den linjära tidsvariabla modellen har använts till att ta fram två regulatorer. En LQ-regulator och en H_∞-regulator. Hur dessa tas fram och vilka problem som finns diskuteras i rapporten. För att kunna se fördelar och nackdelar beträffande prestanda och robusthet har en mängd tester gjort. Testerna visar på olika fördelar hos de olika reglersystemen. Till exempel är det lättare att få bra prestanda med LQ-regulatorn än H_∞-regulatorn om systemet som styrs stämmer bra överens med systemet som använts vid reglerdesignen. H_∞-regulatorn har bättre förmåga att anpassa sig till modellförändringar givet att observatören gör bra skattningar. Det är dock svårt att utnämna en generell vinnare.

Le but de cette thèse est le développement et l'application de différentes méthodes de contrôle pour le contrôle actif du bruit en présence de perturbations incertaines et variables dans le temps. Une conception de contrôleur basée sur un modèle est appliquée et une méthodologie complète pour l'identification du modèle est introduite. Dans ce contexte, un banc d'essai reconfigurable basé sur un silencieux de bruit pour gaines a été conçu et construit. Il est entièrement équipé de capteurs et d'actionneurs afin de tester les algorithmes développés dans diverses configurations.Un schéma contre-réaction feedback est établi pour les cas où des perturbations en bande étroite sont présentes. Sur la base du Principe du Modèle Interne, des contrôleurs linéaires fixes et robustes sont conçus et comparés avec le contrôleur par contre-réaction adaptatif proposé en utilisant un paramétrage Youla-Kučera. Dans le cas où les perturbations présentent des caractéristiques à large bande, un système de rétroaction feedforward est proposé. Cette approche nécessite l'introduction d'un capteur supplémentaire qui crée un couplage positif interne, nécessitant une conception spécifique afin d'éviter d'éventuelles instabilités. Dans ce cadre, les compensateurs adaptatifs IIR et FIR, ainsi que les compensateurs adaptatifs avec paramétrage Youla-Kučera sont comparés.La qualité des modèles estimés pour la conception des contrôles ainsi que les capacités de contrôle elles-mêmes sont illustrées par les performances expérimentales des contrôleurs mis en œuvre sur le banc d'essai pour diverses conditions de configuration des tests
The aim of this thesis is the development and application of different control methods for Active Noise Control in the presence of uncertain and time-varying disturbances. A model-based controller design is applied and a full methodology for model identification is introduced. In this context, a reconfigurable test bench based on a noise silencer for ducts has been designed and built. It is fully equipped with sensors and actuators in order to test the developed algorithms in diverse configurations.A feedback scheme is established for the case where narrowband disturbances are present. Based on the Internal Model Principle, fixed linear and robust controllers are designed and compared with the proposed adaptive feedback controller using a Youla-Kučera parametrization. For the case where disturbances have broadband characteristics, a feedforward scheme is proposed. This approach requires the introduction of an additional sensor which creates an internal positive coupling, requiring a specific design in order to avoid possible instabilities. In this framework, Infinite (IIR) and Finite (FIR) Impulse Responses adaptive feedforward compensators, as well as Youla-Kučera parametrized adaptive feedforward compensators are compared.The estimated models' quality for control design as well as the control capabilities themselves are illustrated by the experimental performance of the controllers implemented on the test bench for various tests setup conditions

Although the finite element method is often applied to analyze the dynamics of structures, its application to large, complex structures can be time-consuming and errors in the modeling process may negatively affect the accuracy of analyses based on the model. System identification techniques attempt to circumvent these problems by using experimental response data to characterize or identify a system. However, identification of structures that are time-varying or nonlinear is problematic because the available methods generally require prior understanding about the equations of motion for the system. Nonlinear system identification techniques are generally only applicable to nonlinearities where the functional form of the nonlinearity is known and a general nonlinear system identification theory is not available as is the case with linear theory. Linear time-varying identification methods have been proposed for application to nonlinear systems, but methods for general time-varying systems where the form of the time variance is unknown have only been available for single-input single-output models. This dissertation presents several general linear time-varying methods for multiple-input multiple-output systems where the form of the time variance is entirely unknown. The methods use the proper orthogonal decomposition of measured response data combined with linear system theory to construct a model for predicting the response of an arbitrary linear or nonlinear system without any knowledge of the equations of motion. Separate methods are derived for predicting responses to initial displacements, initial velocities, and forcing functions. Some methods require only one data set but only promise accurate solutions for linear, time-invariant systems that are lightly damped and have a mass matrix proportional to the identity matrix. Other methods use multiple data sets and are valid for general time-varying systems. The proposed methods are applied to linear time-invariant, time-varying, and nonlinear systems via numerical examples and experiments and the factors affecting the accuracy of the methods are discussed.
Ph. D.

This dissertation is a systematic study of electric power distribution system reliability evaluation and improvement. Reliability evaluation of electric power systems has traditionally been an integral part of planning and operation. Changes in the electric utility coupled with aging electric apparatus create a need for more realistic techniques for power system reliability modeling. This work presents a reliability evaluation technique that combines set theory and Graph Trace Analysis (GTA). Unlike the traditional Markov approach, this technique provides a fast solution for large system reliability evaluation by managing computer memory efficiently with iterators, assuming a single failure at a time. A reconfiguration for restoration algorithm is also created to enhance the accuracy of the reliability evaluation, considering multiple concurrent failures. As opposed to most restoration simulation methods used in reliability analysis, which convert restoration problems into mathematical models and only can solve radial systems, this new algorithm seeks the reconfiguration solution from topology characteristics of the network itself. As a result the new reconfiguration algorithm can handle systems with loops. In analyzing system reliability, this research takes into account time-varying load patterns, and seeks approaches that are financially justified. An exhaustive search scheme is used to calculate optimal locations for Distributed Generators (DG) from the reliability point of view. A Discrete Ascent Optimal Programming (DAOP) load shifting approach is proposed to provide low cost, reliability improvement solutions. As weather conditions have an important effect on distribution component failure rates, the influence of different types of storms has been incorporated into this study. Storm outage models are created based on ten yearsâ worth of weather and power outage data. An observer is designed to predict the number of outages for an approaching or on going storm. A circuit corridor model is applied to investigate the relationship between power outages and lightning activity.
Ph. D.

This dissertation describes the development and modeling of a low-cost, open source, and reliable small fixed-wing unmanned aerial vehicle (UAV) for advanced control implementation. The platform is mostly constructed of low-cost commercial off-the-shelf (COTS) components. The only non-COTS components are the airdata probes which are manufactured and calibrated in-house, following a procedure provided herein. The airframe used is the commercially available radio-controlled 6-foot Telemaster airplane from Hobby Express. The airplane is chosen mainly for its adequately spacious fuselage and for being reasonably stable and sufficiently agile. One noteworthy feature of this platform is the use of two separate low-cost open source onboard computers for handling the data management/hardware interfacing and control computation. Specifically, the single board computer, Gumstix Overo Fire, is used to execute the control algorithms, whereas the autopilot, Ardupilot Mega, is mostly used to interface the Overo computer with the sensors and actuators. The platform supports multi-vehicle operations through the use of a radio modem that enables multi-point communications. As the goal of the development of this platform is to implement rigorous control algorithms for real-time trajectory tracking and distributed control, it is important to derive an appropriate flight dynamic model of the platform, based on which the controllers will be synthesized. For that matter, reasonably accurate models of the vehicle, servo motors and propulsion system are developed. Namely, the output error method is used to estimate the longitudinal and lateral-directional aerodynamic parameters from flight test data. The moments of inertia of the platform are determined using the simple pendulum test method, and the frequency response of each servomotor is also obtained experimentally. The Javaprop applet is used to obtain lookup tables relating airspeed to propeller thrust at constant throttle settings. Control systems are also designed for the regulation of this UAV along real-time trajectories. The reference trajectories are generated in real-time from a library of pre-specified motion primitives and hence are not known a priori. Two concatenated primitive trajectories are considered: one formed from seven primitives exhibiting a figure-8 geometric path and another composed of a Split-S maneuver that settles into a level-turn trim trajectory. Switched control systems stemming from l2-induced norm synthesis approaches are designed for discrete-time linearized models of the nonlinear UAV system. These controllers are analyzed based on simulations in a realistic operational environment and are further implemented on the physical UAV. The simulations and flight tests demonstrate that switched controllers, which take into account the effects of switching between constituent sub-controllers, manage to closely track the considered trajectories despite the various modeling uncertainties, exogenous disturbances and measurement noise. These switched controllers are composed of discrete-time linear sub-controllers designed separately for a subset of the pre-specified primitives, with the uncertain initial conditions, that arise when switching between primitives, incorporated into the control design.
Ph. D.

A new approach to the evaluation of the reliability of electrical systems is presented. In this approach a Graph Trace Analysis based approach is applied to integrated system models and reliability analysis. The analysis zones are extended from the traditional power system functional zones. The systems are modeled using containers with iterators, where the iterators manage graph edges and are used to process through the topology of the graph. The analysis provides a means of computationally handling dependent outages and cascading failures. The effects of adverse weather, time-varying loads, equipment age, installation environment, operation conditions are considered. Sequential Monte Carlo simulation is used to evaluate the reliability changes for different system configurations, including distributed generation and transmission lines. Historical weather records and loading are used to update the component failure rates on-the-fly. Simulation results are compared against historical reliability field measurements. Given a large and complex plant to operate, a real-time understanding of the networks and their situational reliability is important to operational decision support. This dissertation also introduces using an Integrated System Model in helping operators to minimize real-time problems. A real-time simulation architecture is described, which predicts where problems may occur, how serious they may be, and what is the possible root cause.
Ph. D.

Dissertation (Ph.D..) -- Worcester Polytechnic Institute.
Keywords: structural health monitoring; wavelet transform; time varying vibration modes; instantaneous modal parameters. Includes bibliographical references (p.181-186).

The research is motivated by real applications, such as pasteurization plant, water networks and autonomous system, which each of them require a specific control system to provide proper management able to take into account their particular features and operating limits in presence of uncertainties related to their operation and failures from component breakdowns. According to that most of the real systems have nonlinear behaviors, it can be approximated them by polytopic linear uncertain models such as Linear Parameter Varying (LPV) and Takagi-Sugeno (TS) models. Therefore, a new economic Model Predictive Control (MPC) approach based on LPV/TS models is proposed and the stability of the proposed approach is certified by using a region constraint on the terminal state. Besides, the MPC-LPV strategy is extended based on the system with varying delays affecting states and inputs. The control approach allows the controller to accommodate the scheduling parameters and delay change. By computing the prediction of the state variables and delay along a prediction time horizon, the system model can be modified according to the evaluation of the estimated state and delay at each time instant. To increase the system reliability, anticipate the appearance of faults and reduce the operational costs, actuator health monitoring should be considered. Regarding several types of system failures, different strategies are studied for obtaining system failures. First, the damage is assessed with the rainflow-counting algorithm that allows estimating the component’s fatigue and control objective is modified by adding an extra criterion that takes into account the accumulated damage. Besides, two different health-aware economic predictive control strategies that aim to minimize the damage of components are presented. Then, economic health-aware MPC controller is developed to compute the components and system reliability in the MPC model using an LPV modeling approach and maximizes the availability of the system by estimating system reliability. Additionally, another improvement considers chance-constraint programming to compute an optimal list replenishment policy based on a desired risk acceptability level, managing to dynamically designate safety stocks in flowbased networks to satisfy non-stationary flow demands. Finally, an innovative health-aware control approach for autonomous racing vehicles to simultaneously control it to the driving limits and to follow the desired path based on maximization of the battery RUL. The proposed approach is formulated as an optimal on-line robust LMI based MPC driven from Lyapunov stability and controller gain synthesis solved by LPV-LQR problem in LMI formulation with integral action for tracking the trajectory.
Esta tesis pretende proporcionar contribuciones teóricas y prácticas sobre seguridad y control de sistemas industriales, especialmente en la forma maten ática de sistemas inciertos. La investigación está motivada por aplicaciones reales, como la planta de pasteurización, las redes de agua y el sistema autónomo, cada uno de los cuales requiere un sistema de control específico para proporcionar una gestión adecuada capaz de tener en cuenta sus características particulares y limites o de operación en presencia de incertidumbres relacionadas con su operación y fallas de averías de componentes. De acuerdo con que la mayoría de los sistemas reales tienen comportamientos no lineales, puede aproximarse a ellos mediante modelos inciertos lineales politopicos como los modelos de Lineal Variación de Parámetros (LPV) y Takagi-Sugeno (TS). Por lo tanto, se propone un nuevo enfoque de Control Predictivo del Modelo (MPC) económico basado en modelos LPV/TS y la estabilidad del enfoque propuesto se certifica mediante el uso de una restricción de región en el estado terminal. Además, la estrategia MPC-LPV se extiende en función del sistema con diferentes demoras que afectan los estados y las entradas. El enfoque de control permite al controlador acomodar los parámetros de programación y retrasar el cambio. Al calcular la predicción de las variables de estado y el retraso a lo largo de un horizonte de tiempo de predicción, el modelo del sistema se puede modificar de acuerdo con la evaluación del estado estimado y el retraso en cada instante de tiempo. Para aumentar la confiabilidad del sistema, anticipar la aparición de fallas y reducir los costos operativos, se debe considerar el monitoreo del estado del actuador. Con respecto a varios tipos de fallas del sistema, se estudian diferentes estrategias para obtener fallas del sistema. Primero, el daño se evalúa con el algoritmo de conteo de flujo de lluvia que permite estimar la fatiga del componente y el objetivo de control se modifica agregando un criterio adicional que tiene en cuenta el daño acumulado. Además, se presentan dos estrategias diferentes de control predictivo económico que tienen en cuenta la salud y tienen como objetivo minimizar el daño de los componentes. Luego, se desarrolla un controlador MPC económico con conciencia de salud para calcular los componentes y la confiabilidad del sistema en el modelo MPC utilizando un enfoque de modelado LPV y maximiza la disponibilidad del sistema mediante la estimación de la confiabilidad del sistema. Además, otra mejora considera la programación de restricción de posibilidades para calcular una política ´optima de reposición de listas basada en un nivel de aceptabilidad de riesgo deseado, logrando designar dinámicamente existencias de seguridad en redes basadas en flujo para satisfacer demandas de flujo no estacionarias. Finalmente, un enfoque innovador de control consciente de la salud para vehículos de carreras autónomos para controlarlo simultáneamente hasta los límites de conducción y seguir el camino deseado basado en la maximización de la bacteria RUL. El diseño del control se divide en dos capas con diferentes escalas de tiempo, planificador de ruta y controlador. El enfoque propuesto está formulado como un MPC robusto en línea optimo basado en LMI impulsado por la estabilidad de Lyapunov y la síntesis de ganancia del controlador resuelta por el problema LPV-LQR en la formulación de LMI con acción integral para el seguimiento de la trayectoria.

A conceptual design of an innovative two-axle lightweight railway vehicle for commuter services is carried out at KTH Railway Group. An active wheelset steering is introduced to improve the curving performance of the vehicle, which is one of the critical performance requirements. This thesis aims to improve the steering performance of the active wheelset steering. Look-up tables for estimating time-varying wheel-rail contact parameters are introduced to supervise a simple PID controller of the active steering system in order to improve steering performance. The look-up table (LUT) estimation is focused on time-varying wheel-rail contact parameters, including creep coefficients and contact patch variables due to their direct influence on curving performance and lateral stability of the wheelset. As a result, the estimated longitudinal unit creep forces (UCF) have the potential to supervise the gains determination of PID controller because it can appropriately distinguish running conditions. The estimation of longitudinal UCF is achieved by the combination of the results from the LUT of creep coefficients and the LUT of contact patch variables. The result from longitudinal unit creep force estimation is shifted to the first quadrant to use as critical gain in the Ziegler-Nichols tuning method for the PID controller. The critical oscillation period for PID tuning can be expressed as a function of vehicle speed. Consequently, the PID controller for the active steering system uses time-varying gains with real-time tuning. The proposed control system for active wheelset steering is validated with nine running conditions using SIMPACK and MATLAB/Simulink co-simulation. The proposed control system provides a stable wheelset lateral displacement control regardless of the running condition. The active steering system significantly reduces wheel-rail wear, which demonstrates the effectiveness of the proposed active steering system.
KTH:s Järnvägsgruppen utvecklar en konceptuell design av ett innovativt, två-axligt, lättvikts järnvägsfordon för tunnelbana eller pendeltåg. En aktiv hjuparsstyrning introduceras för att förbättra kurvtagningsförmågan hos fordonet, vilket är ett av de kritiska prestandakraven hos dessa fordon. Det här examensarbetet har som målsättning att förbättra styrningsprestandan av den aktiva hjulsatsstyrningen. För att uppskatta tidsvarierande hjul-rälskontaktparametrar introduceras pre-definierade tabeller (LUT) som en övervakning av en enkel PID-kontroll för det aktiva styrningssystemet, för att förbättra styrprestandan. Uppskattningen som baseras på tabellen fokuserar på tidsberoende hjul-rälsparametrar, inklusive krypkoefficienter och kontaktytans storlek och form. Dessa variabler är i fokus på grund av deras direkta effekt på kurvtagningsförmågan och den laterala stabiliteten hos hjulparet. Den uppskattade longitudinala enhets krypkraften (UCF) har potential att bestämma förstärkningen hos PID-kontrollen på grund av att den, på ett lämpligt sätt, kan skilja mellan olika körtillstånd. Uppskattningen av longitudinell UCF uppnås genom en kombination av resultat för krypkoefficienter och kontaktytavariabler i LUT. Resultaten från den longitudinella UCF-uppskattningen skiftas till den första kvadranten för att användas som kritisk förstärkning i Ziegler-Nichols justeringsmetod för PID-kontroller. Den kritiska oscillationsperioden för PID-justering kan utryckas som en funktion av fordonets hastighet. Utgående från detta använder PID-kontrollen tidsvarierande förstärkning med realtidsjustering för den aktiva styrningen. Det föreslagna kontrollsystemet valideras mot nio körtillstånd med hjälp av SIMPACK och MATLAB/Simulink-simuleringar. Det föreslagna kontrollsystemet tillhandahåller en stabil lateral förflyttning av hjulparet oberoende av körtillstånd. Det aktiva styrsystemet reducerar hjul-räls slitaget signifikant, vilket demonstrerar effektiviteten hos det framtagna aktiva styrsystemet.

Utilisation d'une methode de modelisation due a g. Chavent, consistant a minimiser un critere de moindres carres de sortie. Etude de 3 modeles comportant des parametres variables en fonction de l'etat du systeme ou du temps. Le probleme d'identification est formule comme un probleme d'optimatisation et resolu numeriquement par un algorithme de descente

Non-centralized control schemes for large-scale systems, including energy networks, are more flexible, scalable, and reliable than the centralized counterpart. These benefrts are obtained by having a set of local control!ers, each of which is responsible for a partition of the system, instead of one central entity that controls the whole system. Furthermore,in sorne cases, employing a non­ centralized control structure might be necessary due to the intractability problem of the centralized method.Thus, this thesis is devoted to the study of non-centralized optimization-based control approaches for large-scale energy systems. Mainly,this thesis focuses on the communication and cooperation processes of local controllers, which are integral parts of such schemes. Throughout this thesis,the model predictíve control framework is applied to solve the economic dispatch problem of large-scale energy systems. In a non-centralized architecture, local controllers must cooperatively solve the economic dispatch problem, which is formulated as a convex optimization problem with edge-based coupling constraints, at each time step.Therefore, first, the augmented Lagrangian approach is deployed to decompose the problem and to design two distributed optimization methods, which are iterative and require the local controllers to exchange information with each other at each iteration. lt is then shown that the sequence produced by these methods converges to an optima!solution when sorne cond tions, which include how the controllers must communicate and cooperate, are satisfied. However, in practice, the communication process might not always be perfect,i.e.,the required communication assumption does not hold. In the case of communication link failures, the distributed methods might not be able to compute a solution.Therefore,an information exchange protocol that is based on consensus is designed to overcome this problem. Furthermore, the proposed distributed methods are also further·extended such that they work over random communication networks and asynchronous updates, i.e.,when not all controllers always perform the updates . Under this setup, the convergence and the convergence rate of the algorithms are shown. Additionally, the implementation of these distributed methods to an MPC-based economic dispatch is also presented. The discussion includes the techniques that can be used to reduce the number of iterat ions and the performance of the methods in a numerical study. Considering that the aforementioned methods are comrnunication-intensive, an alternative non-centralized scheme, which provides a trade-off between comrnunication intensity and suboptirnality,is proposed.The scheme consists of repartitioning the network online with the aim of obtaining self-sufficient subsystems, forming coalitions for subsystems that are not self-sufficient,and decomposing the economic dispatch problem of the system into coalition-based subproblems. In this scheme, each subsystem only communicates to the others that belong to the sarne coalition;thus, reducing communication. Especially when all subsystems are self-sufficient, exchanging information is not needed. Finally,a cooperation problem during the implementation of the decisions is discussed. Specifically, sorne subsystems do not cornply with the computed decisions to gain better performance at the cost of deteriorating the performance of the other subsystems.A resilient scheme that can cope with this problem is formulated.lt consists of a stochastic method to robustify the decisions against such adversaria! behavior and an identification and mitigation method that is based on hypothesis testing using Bayesian inference.The proposed scheme, in general,can mitigate the effect of non-
Los esquemas de control no centralizados aplicados a sistemas a gran escala, entre los que se incluyen las redes energéticas, son más flexibles, escalables y fiables que sus equivalentes centralizados. Dichos beneficios pueden obtenerse empleando un conjunto de controladores locales, donde cada uno de ellos es responsable de una parte del sistema, en lugar de una entidad central que controle la totalidad del sistema.Asimismo,el uso de una estructura de control no centralizada podría ser, en algunos casos, necesario, dado el problema de intratabilidad del método centralizado. Por consiguiente, la presente tesis trata sobre el estudio de enfoques de control no centralizados basados en optimización para redes energéticas a gran escala. Principalmente, esta tesis se centra en los procesos de comunicación y cooperación llevados a cabo por los controladores locales , que constituyen partes esenciales de dichos esquemas . A lo largo de esta tesis, el control predictivo basado en modelos se usa para resolver el problema de expedir energia en redes energéticas a gran escala desde un punto de vista económico. En arquitecturas no centralizadas, los controladores locales deben resolver dicho problema de forma cooperativa, el cual se formula como un problema de optimización convexo con restricciones de acoplamiento en los enlaces entre nodos, que debe ser resuelto en cada instante de tiempo. Para ello, el método de Lagrangiano aumentado se utiliza inicialmente para descomponer el problema y diseñar dos métodos de optimización distribuidos , que son iterativos y requieren que los controladores locales intercambien información entre ellos en cada iteración . A continuación, se muestra que la secuencia generada por estos métodos converge a la solución óptima a condición de que se cumplan ciertas condiciones,incluyendo cómo los controladores deben comunicarse y cooperar. Sin embargo, en la práctica,la comunicación no siempre es perfecta, es decir,el supuesto de comunicación requerido no se cumple. En el caso de fallos en los enlaces de comunicación, los métodos distribuidos podrían no ser capaces de proporcionar una solución. Para paliar este problema, se diseña un protocolo de información basado en consenso.l'v1ás aún, los métodos de optimización distribuidos se extienden a fin de que sean capaces de trabajar en redes con comunicaciones aleatorias y actualizaciones asíncronas, es decir,redes en que no todos los controladores realicen las actualizaciones . En esta configuración se muestran la convergencia y el orden de convergencia de dichos algoritmos. Se muestra, además, la implementación de estos métodos en el control predictivo económico basado en modelos para redes energéticas. La discusión incluye las técnicas que pueden usarse para reducir el número de iteraciones, así como el desempeño de los métodos, a través de un estudio numérico. Teniendo en cuenta que los métodos anteriormente mencionados requieren una comunicación intensa,se propone otro esquema no centralizado que proporciona un compromiso entre intensidad de comunicación y suboptimalidad . Dicha estrategia consiste en volver a particionar en línea el sistema con el objetivo de obtener subsistemas autosuficientes,formando coaliciones de subsistemas que no lo sean por separado,y descomponiendo el problema económico de expedición de energía en subproblemas de tipo coalicional. En este esquema ,cada subsistema se comunica únicamente con aquellos otros subsistemas que pertenezcan a la misma coalición, reduciendo asi el tráfico de comunicación. En particular, cuando todos los subsistemas son autosuficientes, el intercambio de información ya no es necesario. Finalmente,se considera el problema de la cooperación durante la implementación de las decisiones Específicamente, algunos subsistemas no acatan las decisiones tomadas con el fin de lograr un desempeño propio superior a expensas de empeorar el desempeño de otros subsistemas. Es por esto que, con el fin de lidiar con este problema, se propone un esquema resiliente, el cual consiste en un método estocástico para hacer las decisiones más robustas frente a tal comportamiento adverso, y un método de identificación y mitigación basado en evaluación de hipótesis usando inferencia bayesiana. En general, el esquema propuesto logra mitigar el efecto de los subsistemas incumplidores sobre el resto, y en un caso concreto, también permite identificar los subsistemas adversos.
Els esquemes de control no centralitzats aplicats a sistemes a gran escala, entre els quals s’inclouen les xarxes energètiques, són més flexibles, escalables i fiables que els seus equivalents centralitzats. Aquests beneficis es poden obtenir fent servir un conjunt de controladors locals, en què cadascun d’ells és responsable d’una part del sistema, en lloc d’una entitat central que controli la totalitat del sistema. Així mateix, l’ús d’una estructura de control no centralitzada podria ser, en alguns casos, necessari, donat el problema d’intractabilitat del mètode centralitzat. Per tant, la present tesi tracta sobre l’estudi d’enfocaments de control no centralitzats basats en optimització per a xarxes energètiques a gran escala. Principalment, aquesta tesi se centra en els processos de comunicació i cooperació duts a terme pels controladors locals, que constitueixen parts essencials d’aquests esquemes. Al llarg d’aquesta tesi, el control predictiu basat en models s’utilitza per a resoldre el problema d’expedició d’energia en xarxes energètiques a gran escala des d’un punt de vista econòmic. En arquitectures no centralitzades, els controladors locals han de resoldre aquest problema de forma cooperativa, formulat com un problema d’optimització convex amb restriccions d’acoblament en els enllaços entre nodes i que ha de ser resolt a cada instant de temps. A tal efecte, el mètode de Lagrangià augmentat s’utilitza inicialment per a descomposar el problema i dissenyar dos mètodes d’optimització distribuïts, que són iteratius i requereixen que els controladors locals intercanviïn informació entre ells a cada iteració. A continuació, es mostra que la seqüència generada per aquests mètodes convergeix a la solució òptima si es compleixen certes condicions, incloent la manera en què els controladors s’han de comunicar i cooperar. No obstant això, a la pràctica, la comunicació no és sempre perfecta, és a dir, el supòsit de comunicació perfecta no es compleix. En el cas de fallades en els enllaços de comunicació, els mètodes distribuïts podrien no ser capaços de proporcionar una solució. Per a resoldre aquest problema, es dissenya un protocol d’informació basat en consens. A més, els mètodes d’optimització distribuïts s’amplien per tal que siguin capaços de treballar en xarxes amb comunicacions aleatòries i actualitzacions asíncrones, és a dir, xarxes en què no tots els controladors realitzin les actualitzacions. En aquestes configuracions es mostren la convergència i l’ordre de convergència d’aquests algoritmes. A més, es mostra també la implementació d’aquests mètodes en el control predictiu econòmic basat en models per a xarxes energètiques. La discussió inclou les tècniques que es poden emprar per a reduir el nombre d’iteracions, així com el rendiment dels mètodes, fent servir un estudi numèric. Tenint en compte que els mètodes anteriorment esmentats requereixen una comunicació intensa, es proposa un altre esquema no centralitzat que proporciona un compromís entre intensitat de comunicació i suboptimalitat. Aquesta estratègia consisteix en tornar a particionar el sistema en línia amb l’objectiu d’obtenir subsistemes autosuficients, formant coalicions de subsistemes que no ho siguin per separat, i descomposant el problema econòmic d’expedició d’energia en subproblemes de tipus coalicional. En aquest esquema, cada subsistema es comunica únicament amb aquells altre subsistemes que pertanyin a la mateixa coalició, reduint així el trànsit de comunicació. En particular, quan tots els sistemes són autosuficients, l’intercanvi d’informació deixa de ser necessari. Finalment, es considera el problema de la cooperació durant la implementació de les decisions. Específicament, alguns subsistemes no acaten les decisions preses amb la finalitat de millorar el propi rendiment a costa de disminuir el d’altres subsistemes. És per això que, a fi de solucionar aquest problema, es proposa un esquema resilient, el qual consisteix en un mètode estocàstic per fer les decisions més robustes davant d’aquest comportament advers, i un mètode d’identificació i mitigació basat en evaluar hipòtesis utilitzant inferència bayesiana. En general, l’esquema proposat aconsegueix mitigar l’efecte que els subsistemes no obedients exerceixen sobre la resta, i en un cas concert, també permet identificar els subsistemes adversos.
ABSTRAKSI (Indfonesian) Skema kendali yang tidak tersentralisasi untuk sistem berskala besar, seperti sistem aringan energi, lebih fleksibel, skalabel, dan reliabel dibandingkan dengan skema tersentralisasi. Keuntungan ini diperoleh dari terdapatnya satu set pengendali lokal, yang hanya bertanggung jawab terhadap satu partisi dari sistem tersebut, daripada jika hanya terdapat satu entitas yang mengendalikan seluruh sistem. Bahkan dalam beberapa sistem, penerapan struktur kendali yang tidak tersentralisasi menjadi keharusan karena adanya permasalahan intraktabilitas dari metode tersentralisasi. Oleh karena itu, disertasi ini bertujuan untuk melakukan studi pada metode kendali berdasarkan optimisasi dengan struktur yang tidak tersentralisasi untuk sistem energi berskala besar. Khususnya, disertasi ini memfokuskan pada proses komunikasi dan kooperasi pengendali‐pengendali lokal, yang merupakan bagian integral dalam skema yang dimaksud. Pada disertasi ini, sistem kontrol prediktif (model predictive control (MPC)) diterapkan untuk menyelesaikan optimisasi economic dispatch pada sistem energi berskala besar. Dalam arsitektur yang tidak tersentralisasi, pengendali‐pengendali lokal harus menyelesaikan permasalahan economic dispatch secara kooperatif. Permasalahan economic dispatch ini diformulasikan sebagai optimisasi yang konveks dan memiliki konstrain terkopling. Oleh karena itu, pendekatan Lagrange yang teraugmentasi diterapkan untuk mendekomposisi permasalahan optimisasi terkait. Pendekatan ini juga digunakan untuk merancang dua metode optimisasi terdistribusi, yang iteratif dan mengharuskan pengendali‐pengendali lokal bertukar informasi satu sama lain pada setiap iterasi. Sekuensi yang dihasilkan dari kedua metode tersebut akan terkonvergensi pada suatu solusi yang optimal apabila beberapa kondisi, yang meliputi bagaimana pengendali harus berkomunikasi dan berkooperasi, terpenuhi. Namun, pada praktiknya, proses komunikasi yang terjadi mungkin tidak selalu sempurna, dalam hal ini asumsi pada proses komunikasi yang dibutuhkan tidak terpenuhi. Pada kasus kegagalan jaringan komunikasi, metode terdistribusi yang dirancang mungkin tidak dapat menemukan solusinya. Oleh karena itu, suatu protokol untuk pertukaran informasi yang berdasarkan pada konsensus dirancang untuk mengatasi permasalahan ini. Selanjutnya, dua metode terdistribusi yang telah dirancang juga dikembangkan lebih jauh sehingga metode‐metode tersebut dapat bekerja pada jaringan komunikasi stokastik dengan proses yang asinkron, yaitu proses dimana tidak semua pengendali selalu melakukan pembaruan. Dalam hal ini, konvergensi dan laju konvergensi dari metode yang dirancang dipertunjukkan. Selain itu, implementasi dari metode terdistribusi pada sistem economic dispatch berbasis MPC juga dibahas. Diskusi pada bagian ini mencakup beberapa teknik yang dapat digunakan untuk mengurangi jumlah iterasi dan performa dari metode‐metode yang dirancang pada suatu studi numerik. Dengan pertimbangan bahwa metode‐metode yang disebut sebelumnya membutuhkan komunikasi yang intensif, maka sebuah skema alternatif, yang memberikan trade‐off antara intensitas komunikasi dan suboptimalitas, juga dirancang. Skema ini terdiri dari repartisi sistem online yang bertujuan untuk mendapatkan subsistemsubsistem yang swasembada, pembentukan koalisi untuk subsistem‐subsistem yang tidak swasembada, dan dekomposisi permasalahan economic dispatch menjadi subproblem berbasis koalisi. Dalam skema ini, tiap subsistem hanya perlu berkomunikasi dengan subsistem‐subsistem lain yang berada pada koalisi yang sama; sehingga mengurangi aliran komunikasi. Jika semua subsistem yang terbentuk swasembada, maka pertukaran informasi tidak dibutuhkan sama sekali. Pada akhirnya, disertasi ini juga membahas mengenai suatu permasalahan koperasi dalam masa implementasi keputusan (solusi). Pada permasalahan kooperasi ini, terdapat beberapa subsistem yang tidak menuruti keputusan (solusi), misalnya dengan tujuan untuk mendapatkan kinerja yang lebih baik dan di saat yang bersamaan memperburuk kinerja subsistem lainnya. Maka, sebuah skema resilien yang dapat mengatasi permasalahan ini dirumuskan. Skema tersebut terdiri dari sebuah metode stokastik untuk merobustifikasi keputusan terhadap perilaku adversari dan sebuah metode identifikasi dan mitigasi yang berdasarkan pada pengujian hipotesis dengan menggunakan inferensi Bayes. Skema yang diusulkan, secara umum, dapat memitigasi pengaruh subsistem yang tidak patuh pada subsistem reguler, dan pada kasus tertentu, juga dapat mengidentifikasi subsistem yang menjadi adversari.

Cette thèse est dédiée à l'analyse de stabilité des systèmes à pas d'échantillonnage variable et à la commande dynamique de l'échantillonnage. L'objectif est de concevoir des lois d'échantillonnage permettant de réduire la fréquence d'actualisation de la commande par retour d'état, tout en garantissant la stabilité du système.Tout d'abord, un aperçu des récents défis et axes de recherche sur les systèmes échantillonnés est présenté. Ensuite, une nouvelle approche de contrôle dynamique de l'échantillonnage, "échantillonnage dépendant de l'état", est proposée. Elle permet de concevoir hors-ligne un échantillonnage maximal dépendant de l'état défini sur des régions coniques de l'espace d'état, grâce à des LMIs.Plusieurs types de systèmes sont étudiés. Tout d'abord, le cas de système LTI idéal est considéré. La fonction d'échantillonnage est construite au moyen de polytopes convexes et de conditions de stabilité exponentielle de type Lyapunov-Razumikhin. Ensuite, la robustesse vis-à-vis des perturbations est incluse. Plusieurs applications sont proposées: analyse de stabilité robuste vis-à-vis des variations du pas d'échantillonnage, contrôles event-triggered et self-triggered, et échantillonnage dépendant de l'état. Enfin, le cas de système LTI perturbé à retard est traité. La construction de la fonction d'échantillonnage est basée sur des conditions de stabilité L2 et sur un nouveau type de fonctionnelles de Lyapunov-Krasovskii avec des matrices dépendant de l'état. Pour finir, le problème de stabilisation est traité, avec un nouveau contrôleur dont les gains commutent en fonction de l'état du système. Un co-design contrôleur/fonction d'échantillonnage est alors proposé

L’ évolution des systèmes radar et de guerre électronique tend à concevoir desrécepteurs numériques possédant des bandes instantanées de plus en plus larges. Cette contraintese reporte sur les Convertisseurs Analogique-Numérique (CAN) qui doivent fournir une fréquenced’échantillonnage de plus en plus élevée tout en conservant une puissance dissipée réduite. Unesolution pour répondre à cette demande est le CAN à Temps Entrelacés (ET-CAN) qui paralléliseM CANs pour augmenter la fréquence d’échantillonnage d’un facteur M tout en restant dansun rapport proportionné avec la puissance dissipée. Cependant, les performances dynamiquesdes ET-CANs sont réduites par des défauts d’entrelacements liés à des différences de processusde fabrication, de leur tension d’alimentation et des variations de température. Ces défautspeuvent être modélisés comme issus des disparités d’offsets, de gains ou décalages temporels etglobalement comme issus des disparités de réponses fréquentielles. Ce sont sur ces dernièresdisparités, moins traitées dans la littérature, que portent nos travaux. L’objectif est d’étudierces disparités pour en déduire un modèle et une méthode d’estimation puis, de proposer desméthodes de compensation numérique qui peuvent être implémentées sur une cible FPGA.Pour cela, nous proposons un modèle général des disparités de réponses fréquentielles desET-CANs pour un nombre de voies M quelconques. Celui-ci mélange une description continuedes disparités et une description discrète de l’entrelacement, résultant sur une expression desdéfauts des ET-CANs comme un filtrage à temps variant périodique (LPTV) du signal analogiqueéchantillonné uniformément. Puis, nous proposons une méthode d’estimation des disparitésdes ET-CANs basée sur les propriétés de corrélation du signal en sortie du modèle, pour Mvoies quelconques. Ensuite, nous définissions une architecture de compensation des disparitésde réponses fréquentielles des ET-CANs et nous étudions ses performances en fonction de sesconfigurations et du signal en entrée. Nous décrivons une implémentation de cette architecturepour M=4 voies entrelacées sur cible FPGA et nous étudions les ressources consommées afin deproposer des pistes d’optimisation. Enfin, nous proposons une seconde méthode de compensationspécifique au cas M=2 voies entrelacées, dérivée de la première mais travaillant sur le signalanalytique en sortie d’un ET-CAN et nous la comparons à une méthode similaire de l’état del’art
The evolution of radar and electronic warfare systems tends to develop digitalreceivers with wider bandwidths. This constraint reaches the Analog to Digital Converters(ADC) which must provide a sample rate higher and higher while maintaining a reducedpower dissipation. A solution to meet this demand is the Time-Interleaved ADC (TIADC)which parallelizes M ADCs, increasing the sampling frequency of an M factor while still ina proportionate relation to the power loss. However, the dynamic performance of TIADCsare reduced by errors related to the mismatches between the sampling channels, due to themanufacturing processes, the supply voltage and the temperature variations. These errors canbe modeled as the result of offset, gain and clock-skew mismatches and globally as from thefrequency response mismatches. It is these last mismatches, unless addressed in the literaturethat carry our work. The objective is to study these errors to derive a model and an estimationmethod then, to propose digital compensation methods that can be implemented on a FPGAtarget.First, we propose a general TIADC model using frequency response mismatches for any Mchannel number. Our model merge a continuous-time description of mismatches and a discretetimeone of the interleaving process, resulting in an expression of the TIADC errors as a linearperiodic time-varying (LPTV) system applied to the uniformly sampled analog signal. Then,we propose a method to estimate TIADC errors based on the correlation properties of theoutput signal for any M channel. Next, we define a frequency response mismatch compensationarchitecture for TIADC errors and we study its performance related to its configuration and theinput signal. We describe an FPGA implementation of this architecture for M=4 interleavedchannels and we study the resources consumption to propose optimisations. Finally, we proposea second compensation method, specific to M=2 interleaved channels and derived from the firstone, but working on the analytical signal from the TIADC output and we compare it to a similarstate-of-the-art method

Les interfaces haptiques à retour d'effort sont des dispositifs robotiques capables deproduire des forces à destination de l'utilisateur en téléopération et en réalité virtuelle. L'utilisation d'interface à retour d'effort en Conception Assistée par Ordinateur (CAO) offre de nouvelles perspectives pour la création et la conception de formes 3D grâce à une interactivité à la fois visuelle et kinesthésique. Elles permettent à la fois de visualiser, de manipuler en temps réel des objets virtuels et d'en ressentir les efforts (liés aux contacts, à la déformation, etc.).Les travaux présentés dans cette thèse contribuent au développement d'interfaces àretour d'effort pour répondre au mieux aux besoins de la CAO. Dans ce mémoire, l'accent est placé sur la problématique de la stabilité et son exploitation pour la commande de l'interface mais aussi pour la conception électromécanique. L'ensemble des travaux porte sur une interface à un degré de liberté.Dans un premier temps, différents facteurs liés au système mécanique (amortissement, modes vibratoires) et à l'environnement virtuel (échantillonnage, retard. . .) agissant sur la stabilité d'une interface sont mis en évidence à l'aide de critères fréquentiels. Ensuite, la conception d'une interface (choix et dimensionnement des composants) est ramenée sous forme d'un problème d'optimisation incluant une contrainte liée à la stabilité (en termes de domaine d'utilisation) et un critère de maximisation de la transparence (en termesd'inertie du dispositif).Dans un second temps, l'architecture de commande des dispositifs haptiques est étudiée. À l'aide d'une nouvelle condition de stabilité asymptotique pour les systèmes en temps discret à retard variable et en utilisant un observateur d'état augmenté comme alternative à l'utilisation standard de la méthode des différences finies arrières, la synthèse d'une nouvelle architecture de commande est proposée.La dernière partie du mémoire aborde la description du banc d'essai expérimental développé pendant le travail de thèse ainsi que les résultats des tests réalisés.

La modélisation du vivant, en particulier la modélisation de l'activité cardiaque, est devenue un défi scientifique majeur. Le but de cette thématique est de mieux comprendre les phénomènes physiologiques et donc d'apporter des solutions à des problèmes cliniques. Nous nous intéressons dans cette thèse à la modélisation et à l'étude numérique de l'activité électrique du cœur, en particulier l'étude des électrocardiogrammes (ECGs). L'onde électrique dans le cœur est gouvernée par un système d'équations de réaction-diffusion appelé modèle bidomaine ce système est couplé à une EDO représentant l'activité cellulaire. Afin simuler des ECGs, nous tenons en compte la propagation de l'onde électrique dans le thorax qui est décrite par une équation de diffusion. Nous commençons par une démonstrer l'existence d'une solution faible du système couplé cœur-thorax pour une classe de modèles ioniques phénoménologiques. Nous prouvons ensuite l'unicité de cette solution sous certaines conditions. Le plus grand apport de cette thèse est l'étude et la simulation numérique du couplage électrique cœur-thorax. Les résultats de simulations sont représentés à l'aide des ECGs. Dans une première partie, nous produisons des simulations pour un cas normal et pour des cas pathologiques (blocs de branche gauche et droit et des arhythmies). Nous étudions également l'impact de certaines hypothèses de modélisation sur les ECGs (couplage faible, utilisation du modèle monodomaine, isotropie, homogénéité cellulaire, comportement résistance-condensateur du péricarde,. . . ). Nous étudions à la fin de cette partie la sensibilité des ECGs par apport aux paramètres du modèle. En deuxième partie, nous effectuons l'analyse numérique de schémas du premier ordre en temps découplant les calculs du potentiel d'action et du potentiel extérieur. Puis, nous combinons ces schémas en temps avec un traîtement explicite du type Robin-Robin des conditions de couplage entre le cœur et le thorax. Nous proposons une analyse de stabilité de ces schémas et nous illustrons les résultats avec des simulations numériques d'ECGs. La dernière partie est consacrée à trois applications. Nous commençons par l'estimation de certains paramètres du modèle (conductivité du thorax et paramètres ioniques). Dans la deuxième application, qui est d'originie industrielle, nous utilisons des méthodes d'apprentissage statistique pour reconstruire des ECGs à partir de mesures ('électrogrammes). Enfin, nous présentons des simulations électro-mécaniques du coeur sur une géométrie réelle dans diverses situations physiologiques et pathologiques. Les indicateurs cliniques, électriques et mécaniques, calculés à partir de ces simulations sont très similaires à ceux observés en réalité.

碩士
明志科技大學
電機工程研究所
101
With the gradually maturity of smart grid concepts and norms, the application of automatic meter reading technology and equipment are prevalent. Automatic meter reading technology is convenient and beneficial to reduce manpower, but the time stamp between the record center and watt-hour meter system time is probably asynchronous. The error of watt-hour meter record may be caused by the offset of the system timestamp. Additionally, the information transmitted from Watt-hour meter to record center may be stolen and falsified. To resolve these problems, the aim of this thesis is to develop an encryption system platform exemplified by Samsung S3C6410 ARM11, which encompassed the Linux embedded system with Qt as the core of the proposed system framework. Through the changes of the time factor consistent with Data Encryption Standard (DES) encryption method, the information of watt-hour meters has been protected. The method combined Encryption and decryption based on the precision time synchronization protocol (PTP) could meet the requirement of the system time synchronization. By the use of I/O pin trigger, Encryption and decryption can get the same encryption and decryption key at the same time. The encrypted watt-hour meter information can change with the trigger timing and time variation. The system included a touch trigger button, encryption, decryption information display, encryption and decryption status, which employed text file records for reference. The evidenced result revealed that the proposed system framework not only protect the security of watt-hour meter information, but also synchronize the time clock between the record center and watt-hour meter system time.

Novel methods of system identification are developed in this dissertation. First set of methods are designed to realize time varying linear dynamical system models from input-output experimental data. The preliminary results obtained in a recent paper by the author are extended to establish a new algorithm called the Time Varying Eigensystem Realization Algorithm (TVERA). The central aim of this algorithm is to obtain a linear, time varying, discrete time model sequence of the dynamic system directly from the input-output data. Important results relating to concepts concerning coordinate systems for linear time varying systems are developed (discrete time theory) and an intuitive understanding of equivalent realizations is provided. A procedure to develop first few time step models is detailed, providing a unified solution to the time varying identification problem. The practical problem of identifying the time varying generalized Markov parameters required for TVERA is presented as the next result. In the process, we generalize the classical time invariant input output AutoRegressive model with an eXogenous input (ARX) models to the time varying case and realize an asymptotically stable observer as a byproduct of the calculations. It is further found that the choice of the generalized time varying ARX model (GTV-ARX) can be set to realize a time varying dead beat observer. Methods to use the developed algorithm(s) in this research are then considered for application to the identification of system models that are bilinear in nature. The fact that bilinear plant models become linear for constant inputs is used in the development of an algorithm that generalizes the classical developments of Juang. An intercept problem is considered as a candidate for application of the time varying identification scheme, where departure motion dynamics model sequence is calculated about a nominal trajectory with suboptimal performance owing to the presence of unstructured perturbations. Control application is subsequently demonstrated. The dynamics of a particle in a rotating tube is considered next for identification using the time varying eigensystem realization algorithm. Continuous time bilinear system identification method is demonstrated using the particle example and the identification of an automobile brake model.

碩士
明志科技大學
電機工程研究所
100
With the advancement of technology, the trends of reading a power meter have been moved from labor to automated meter reading. The advantages of automated meter reading are lower cost and less error. This thesis proposed a system to ensure the ciphertext transmutation that can prevent the data from stolen by prying eyes. For reacting the principle of time-of-use rate charge according to period, we need a set of accurate time synchronization to assure the basis of the charge. Furthermore, adopting the concept of time and the use of the change of time embedded within this system increases the diversity of ciphertext and make the code-breaking impossible. To combine the way of encryption with time, the concept of time synchronization is materialized with IEEE 1588 (Precision Time Protocol, PTP) which uses the clock rate of master and slave. Time would be synchronized by using an equation to continue master’s oscillation frequency and fine tuning. With PTP, the timestamp of two connected computer systems can be synchronized such that the encryption and decipher can be assured and avoided losing the efficacy of online transmitting information. This system adopts LabVIEW combined with Caesar Cipher by Rail Fence Cipher to make encryption and realized the concept of the change of time.

碩士
國立中興大學
土木工程學系
90
This paper deals with the applicability of SRIM system identification technique together with time moving windows (called WSRIM) to evaluate the time-varying dynamic properties of a building to assess its damage based on real earthquake records considering soil-structure interaction effect. Successive short segments of input and output signals are selected and the SRIM system identification technique is applied to identify the real-time structural properties during that segment of time. Both numerical simulations and real earthquake response measurements from several building floors and foundations are utilized to verify the accuracy of the proposed time-varying system identification technique. The seven-story Civil and Environmental Engineering Department Building in National Chung-Hsing University is the only instrumented building in Central Taiwan. It experienced moderate structural damage during the 921 Chi-Chi earthquake. This paper is to evaluate the time-varying structural modal parameters of this school building based on the acceleration records during 921 Chi-Chi earthquake main shock and its after-shock. It is proved that the proposed technique is useful for real-time dynamic property assessment of buildings.

碩士
東海大學
數學系
84
In this thesis, we consider an uniformly asymptotically stable linear time varying system G with McMillan degree n, find a stable system $\hat{G}$with McMillan degree degree k which is less then n such that the difference betweenG and $\hat{G}$ under the Hankel norm is minimized.Furthermore, we obtainthe Nehari theorem of time-varying system, and the computation of the Hankel normin linear time varying system and nonlinear time invariant system.

Real-time rendering of static volumetric data is generally known to be a memory and computationally intensive process. With the advance of graphic hardware, especially GPU, it is now possible to do this using desktop computers. However, with the evolution of real-time CT and MRI technologies, volumetric rendering is an even bigger challenge. The first one is how to reduce the data transmission between the main memory and the graphic memory. The second one is how to efficiently take advantage of the time redundancy which exists in the time-varying volumetric data. Most previous researches either focus on one problem or the other. In this thesis, we implemented a system which efficiently deals with both of the challenges. We proposed an optimized compression scheme that explores the time redundancy as well as space redundancy of time-varying volumetric data. The compressed data is then transmitted to graphic memory and directly rendered by GPU, so the data transfer between main memory and graphic memory is significantly reduced. With our implemented system, we successfully reduce more than half of the time of transferring the whole data directly. We also compare our proposed compression scheme with the one without exploiting time redundancy. The optimized compression scheme shows a reduce compression distortion over time. With usability, portability and extensibility in mind, the implemented system is also quite flexible.

碩士
國立中山大學
電機工程學系
87
The design of state feedback controllers and observers are proposed in this thesis for a class of MIMO linear systems with uncertainties and time varying delays. By using Lyapunov stability theorem, a sufficient condition is found for computing the state feedback gain of controllers and the gain of observers in order to stabilize the closed-loop systems in spite of the existence of parameters variations. This sufficient condition is fulfilled by two linear matrices inequalities (LMIs), which can be solved easily by utilizing the software package LMI Control Toolbox of Matlab. The asymptotic stability of the closed-loop system is guaranteed if the solution of LMIs exist.

碩士
國立臺灣大學
土木工程學研究所
100
For improving the resistance of the structure to against the earthquake, the development of structural control becomes an important issue in civil engineering. Structural control can be classified into three types: Passive control, Active control and Semi-active control. The definition of Active control and Semi-active control is using the device installed in the structure which could adjust the behavior by input order to change the dynamic characteristic of the structure. Therefore, applying an ideal control algorithm to compute the input order is the core of the structural control technique. LQR control is one of the significant control algorithms. The design of the LQR controller is depend on the system’s information. However the control effeteness will be poor when the system is time-varying. The purpose of this research is trying to improve the adaptive ability of the LQR controller by combining the system identification technique. And the controller could update the system information of the time-varying system to reform the original LQR controller’s effeteness. The research designed an adaptive controller which is different from the original LQR controller for time-varying system. First in Chapter 2 will introduce the LQR algorithm and to verify the control superiority by a 2 DOFs connected structure control experiment. Then in Chapter 3 we will mention about the system identification algorithm: Subspace Identification which could identify the system information including the natural frequencies and stiffness matrix precisely. In Chapter 4 we combined these two algorithms and design two methods to create the adaptive controller. One of the methods is System Compensator which is used to compensate the reduction of the system’s stiffness by increasing the control force and make the time-varying system behaves like a healthy system. Another method is Gain Switcher which will switch an optimal control gain corresponded to the level of stiffness reduction of the time-varying system. Finally, we used Simulink to simulate the time-varying systems responses under these two adaptive control methods with the mathematic model of MR damper to verify the effeteness. By updating the system’s information using subspace identification, the two adaptive controllers reduced the displacement responses ideally.

碩士
國立高雄應用科技大學
機械工程系
106
This thesis studies the optimal control of wind turbine system with time-varying uncertainties. The optimal feedback gain matrix and the optimal state estimation gain matrix are designed by using the LQG optimal control theory and the Hybrid Taguchi-Genetic Algorithm(HTGA). A sufficient condition in terms of linear matrix inequalities (LMIs) is employed to guarantee that the resulting control system is asymptotically stable in the presence of time-varying uncertainties. Finally a simulation of a wind turbine system is given to demonstrate the use of the design method. The result shows that this designed closed loop system can effectively achieve the desired rotational speed and ensure its stability in the presence of time-varying uncertainties.

碩士
龍華科技大學
機械工程系碩士班
107
In traditional adaptive control, the gradient descent method or least square method is used to estimate the parameters of a time-varying system. The singularity problem in numerical analysis is easily caused due to the errors of numerical rounding and external environmental disturbances in computer calculation, which will affect the response and stability of the closed-loop control system. In this paper, a neural network adaptive controller is proposed. The parameters of a time-varying system are estimated online by using the neural network controller. The control parameters of the self-tuning regulator are calculated by using the pole assignment method. Finally, the experimental results show that the neural network adaptive controller has great stability and fault-tolerance in numerical analysis when estimating the parameters of a highly uncertain time-varying system. Moreover, the stability time, overshoot and mean square error are better than the traditional self-tuning regulator, which proves that the proposed neural network adaptive controller has excellent response characteristics and robustness.

The main topic of this thesis is time-varying optimization, which studies algorithms that can track optimal trajectories of optimization problems that evolve with time. A typical time-varying optimization algorithm is implemented in a running fashion in the sense that the underlying optimization problem is updated during the iterations of the algorithm, and is especially suitable for optimizing large-scale fast varying systems. Motivated by applications in power system operation, we propose and analyze first-order and second-order running algorithms for time-varying nonconvex optimization problems. The first-order algorithm we propose is the regularized proximal primal-dual gradient algorithm, and we develop a comprehensive theory on its tracking performance. Specifically, we provide analytical results in terms of tracking a KKT point, and derive bounds for the tracking error defined as the distance between the algorithmic iterates and a KKT trajectory. We then provide sufficient conditions under which there exists a set of algorithmic parameters that guarantee that the tracking error bound holds. Qualitatively, the sufficient conditions for the existence of feasible parameters suggest that the problem should be "sufficiently convex" around a KKT trajectory to overcome the nonlinearity of the nonconvex constraints. The study of feasible algorithmic parameters motivates us to analyze the continuous-time limit of the discrete-time algorithm, which we formulate as a system of differential inclusions; results on its tracking performance as well as feasible and optimal algorithmic parameters are also derived. Finally, we derive conditions under which the KKT points for a given time instant will always be isolated so that bifurcations or merging of KKT trajectories do not happen. The second-order algorithms we develop are approximate Newton methods that incorporate second-order information. We first propose the approximate Newton method for a special case where there are no explicit inequality or equality constraints. It is shown that good estimation of second-order information is important for achieving satisfactory tracking performance. We also propose a specific version of the approximate Newton method based on L-BFGS-B that handles box constraints. Then, we propose two variants of the approximate Newton method that handle explicit inequality and equality constraints. The first variant employs penalty functions to obtain a modified version of the original problem, so that the approximate Newton method for the special case can be applied. The second variant can be viewed as an extension of the sequential quadratic program in the time-varying setting. Finally, we discuss application of the proposed algorithms to power system operation. We formulate the time-varying optimal power flow problem, and introduce partition of the decision variables that enables us to model the power system by an implicit power flow map. The implicit power flow map allows us to incorporate real-time feedback measurements naturally in the algorithm. The use of real-time feedback measurement is a central idea in real-time optimal power flow algorithms, as it helps reduce the computation burden and potentially improve robustness against model mismatch. We then present in detail two real-time optimal power flow algorithms, one based on the regularized proximal primal-dual gradient algorithm, and the other based on the approximate Newton method with the penalty approach.

碩士
國立高雄應用科技大學
機械與精密工程研究所
103
This paper proposes a robust H∞ control approach for a class of H∞ Control of Satellite Attitude Control System with Time-Varying Uncertainties. In the approach, weighting functions for loop shaping are first chosen to combine with the original system such that a generalized plant is formed. Then, for generalized plant, a controller is obtained by using H∞ control method. The Hybrid Taguchi-Genetic Algorithm(HTGA) is employed to find the optimal gains of the weighting functions which will lead to a stabilizing H∞ controller. Then, a sufficient condition in terms of linear matrix inequalities(LMIs) is employed to guarantee that the resulting control system is asymptotically stable in the presence of time-varying uncertainties. Finally, assimilation example of a Satellite Attitude Control System is given to demonstrate the use of the design approach. The results show that the designed H∞ controller can efficiently achieve the desired control for atellite Attitude System and ensure its stability in the presence of time-varying uncertainties.

碩士
國立高雄應用科技大學
機械與精密工程研究所
102
This paper proposes a robust control approach for a class of Electro-hydraulic Position system with time-varying uncertainties. In the approach, weighting functions for loop shaping are first chosen to combine with the original system such that a generalized plant is formed. Then, for the generalized plant, a controller is obtained by using control method. The Hybrid Taguchi-Genetic Algorithm (HTGA) is employed to find the optimal gains of the weighting functions which will lead to a stabilizing controller. Then, a sufficient condition in terms of linear matrix inequalities (LMIs) is employed to guarantee that the resulting control system is asymptotically stable in the presence of time-varying uncertainties. Finally, a simulation example of a position control system of Electro-hydraulic is given to demonstrate the use of the design approach. The results show that the designed controller can efficiently achieve the desired position for Electro-hydraulic system and ensure its stability in the presence of time-varying uncertainties.

碩士
國立高雄第一科技大學
運輸倉儲營運所
93
The system of logistics distribution is one of the key functions of distribution center. Operation, the major source of D.C. and the operation in D.C. stressed the things that how to use the vehicles effectively and decided the figure of the most economics driving line. Let production send the right quantity to the right position for satisfying the customer’s demand to reach the perfect order. Nowadays the traffic in Taiwan metropolis is heavily and driving, parking and loading are difficultly, which make the complexity of delivering problems more deeply. This study analyzes a different case of the Vehicle Routing Problem (VRP), which is including the time-varying link weight. In real world, a link travel time of a network is changing time to time. That means different departure time of the same route will generate different travel time. How to dispatch vehicles to serve customers and decide the order of services are needed to reconsider under this situation. Moreover, most traditional VRP assume straight-line connection between any two nodes rather than talk about the path selection. In this research, it is also discussed. A heuristic algorithm, which is greedy algorithm, is introduced for solving this VRP. The concept of greedy algorithm is trying to serve as more customers as one vehicle can. In addition, an application is made to illustrate the solution of this algorithm. This application demonstrates a user interface (UI) of solving VRP and using the map of Taipei city as study object.